Hydrogeochemical Characteristics and Quality Assessment of Surface Water in an Agricultural Area in Equatorial Africa: The Mungo River Basin, South West Cameroon, Central Africa

摘要

The Mungo River and its tributaries represent the major sources of water supply for agriculture and drinking purposes for the Douala city and the south western agricultural region of Cameroon. In this study, the surface water hydrochemistry was investigated at 12 locations to determine the hydrochemical and heavy metals characteristics and to assess the suitability for drinking and irrigational purposes. Results of water samples collected along the main channel and tributaries showed that the major ions were dominated by Ca2+ > Na+ > Mg2+ > K+ > NH4+ and > HCO3- > SO42- > Cl- > F- > PO43- , with concentrations varying between 0 to 60 mg/l. Heavy metal concentrations were relatively weak, dominated by Fe > Mn > As > Cd > Zn > Se. The main hydrochemical facies types revealed primarily 52% Ca-Na-HCO3 and 48% Ca-Mg-HCO3. Base on Gibbs diagram and relative ion ratios, the hydrochemical characteristics are derived from weathering of silicate rocks and atmospheric source. The influence of anthropogenic factors including agro-industrial activities on the hydrochemical characteristics was less marked. The chemical composition of the water samples was compared with the drinking water standards and only the concentration of Fe was above the WHO guide limits in a single sample at Passi. The evaluation of the water quality for irrigation showed that 95% of water samples are suitable for irrigation in almost all soil types. According to the water quality index (HPI, HEI and Cd), this water is considered of excellent quality for consumption. The results provide a preliminary database for sustainable management of water resource in the Mungo River basin.